1. Field of the Invention
The present application relates to an optical transceiver, in particular, the present application relates to an optical transceiver capable of performing the coherent optical communication and a method of assemble the optical transceiver.
2. Background Arts
As the mass of the information to be transmitted in the optical communication system drastically increases, new and advanced techniques to expand the transmission capacity has been requested in the field. The coherent system is one of solutions. In the coherent communication, the phase of the light in addition to or substituted from the amplitude of the light becomes the unit of the information. An optical transceiver implemented within the coherent system is necessary to install a local optical beam in addition to an optical signal to be transmitted. The local optical beam is used for recovering the information contained in the optical signal received by the optical transceiver. Accordingly, the optical transceiver is necessary to install, in addition to an optical transmitter and an optical receiver, an optical source to generate the local optical beam, an optical modulator to modulate an optical signal output from the optical source, and complicated electronic circuits to recover the phase information contained in the optical signal. Moreover, when the optical communication system also utilizes the polarization of the transmitted light as the unit of the information, the optical transceiver is necessary to install components above twice as much as that when the polarization is not utilized.
On the other hand, an apparatus or equipment implemented within the communication system has continuously and eagerly requested to make a physical size thereof in compact as long as possible. Accordingly, an optical transceiver used in the coherent communication system, which is often called as a coherent optical transceiver, is necessary to install a lot of optical and electrical components within a compact housing. Various assembling techniques are required to meet such requests.